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Bet hedging in a guild of desert annuals
1Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 95721, USA. venable@email.arizona.edu
Ecology
|June 1, 2007
Summary
Organisms use evolutionary bet hedging to reduce long-term risk, even if it lowers short-term reproduction. A 22-year study confirmed that desert plants with higher demographic variation exhibit delayed germination, a bet hedging strategy.
Area of Science:
- Evolutionary biology
- Ecology
- Life history theory
Background:
- Evolutionary bet hedging is a strategy where organisms reduce short-term reproductive success for long-term risk management.
- Theoretical models support bet hedging, with dormancy in microbes and weeds as examples.
- Empirical data linking demographic variation to bet hedging traits in natural environments have been scarce.
Purpose of the Study:
- To test the evolutionary bet hedging hypothesis using long-term demographic data.
- To investigate the relationship between delayed germination and demographic risk in desert annual plants.
- To determine if reproductive success sensitivity to environmental variation correlates with bet hedging traits.
Main Methods:
- Analysis of a 22-year dataset on demographic variation for 10 species of desert annual plants.
- Quantification of reproductive success variation (survival and fecundity).
- Correlation analysis between germination fraction, demographic variation, and precipitation sensitivity.
Main Results:
- A significant negative association was found between demographic variation and average germination fraction across species.
- Species with greater demographic variation exhibited lower average germination fractions, supporting bet hedging.
- Higher long-term demographic variation was linked to greater sensitivity of reproductive success to annual precipitation changes.
Conclusions:
- The study provides definitive empirical evidence for the evolutionary bet hedging life history prediction.
- Delayed germination in desert annuals serves as an effective bet hedging strategy against demographic risk.
- Environmental stochasticity, particularly precipitation, is a key driver shaping bet hedging strategies in these species.
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